#include "mpi.h"
#include <mpi.h>
#include <getopt.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <malloc.h>
#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>
#include <limits.h>

static void print_char_buf(char *buf_name, char *buf, int64_t buf_len)
{
    int i;

    printf("print_char_buf: %s\n", buf_name);
    for (i = 0; i < buf_len; i++)
    {
        printf("%c ", buf[i]);
        if (((i + 1) % 10) == 0)
            printf("\n");
        else if (((i + 1) % 5) == 0)
            printf("  ");
    }
    printf("\n");
}

char correct_buf[] = {'a', '_', 'b', 'c', '_', '_', '_', '_', 'd', '_', 
		      'e', 'f', 'g', '_', 'h', 'i', 'j', '_', 'k', 'l',
		      '_', '_', '_', '_', 'm', '_', 'n', 'o', 'p', '_',
		      'q', 'r'};

#define COUNT 2
int main(int argc, char **argv)
{
    int myid, numprocs, i;
    char *mem_buf = NULL, *unpack_buf = NULL;
    MPI_Datatype tmp_dtype, mem_dtype;
    MPI_Aint mem_dtype_ext = -1;
    int mem_dtype_sz = -1;
    int mem_buf_sz = -1, unpack_buf_sz = -1, buf_pos = 0;

    int blk_arr[COUNT] = {1, 2};
    int dsp_arr[COUNT] = {0, 2};

    MPI_Init(&argc, &argv);
    MPI_Comm_rank(MPI_COMM_WORLD, &myid);
    MPI_Comm_size(MPI_COMM_WORLD, &numprocs);

    /* Creating the datatype to use for unpacking */
    MPI_Type_indexed(COUNT, blk_arr, dsp_arr,
                     MPI_CHAR, &tmp_dtype);
    MPI_Type_commit(&tmp_dtype);
    MPI_Type_indexed(COUNT, blk_arr, dsp_arr,
                     tmp_dtype, &mem_dtype);
    MPI_Type_commit(&mem_dtype);

    MPI_Type_size(mem_dtype, &mem_dtype_sz);
    MPI_Type_extent(mem_dtype, &mem_dtype_ext);

    mem_buf_sz = 2 * mem_dtype_ext;
    unpack_buf_sz = 2 * mem_dtype_sz;
    if ((mem_buf = (char *) malloc(mem_buf_sz)) == NULL)
    {
	fprintf(stderr, "malloc mem_buf of size %d failed\n", mem_buf_sz);
	return -1;
    }
    memset(mem_buf, '_', mem_buf_sz);
    if ((unpack_buf = (char *) malloc(unpack_buf_sz)) == NULL)
    {
	fprintf(stderr, "malloc unpack_buf of size %d failed\n", 
		unpack_buf_sz);
	return -1;
    }
    
    for (i = 0; i < mem_buf_sz; i++)
	unpack_buf[i] = 'a' + i;
    
    /* Print out before/after unpacking and what I think the correct
     * result should be. */
    print_char_buf("mem_buf before unpack", mem_buf, 2 * mem_dtype_ext);

    MPI_Unpack(unpack_buf, unpack_buf_sz, &buf_pos, 
	       mem_buf, 2, mem_dtype, MPI_COMM_SELF);

    print_char_buf("mem_buf after unpack", mem_buf, 2 * mem_dtype_ext);
    print_char_buf("my version of the correct buffer",
		   correct_buf, 2 * mem_dtype_ext);

    return 0;
}